Color reactive papers which have been chemically coated and/or impregnated with a reagent on a base substrate are individually known in the art. These reagent coated/impregnated papers may be utilized to indicate the presence of a particular substance or compound in the air. Gas reactive papers which alter color in the presence of a target gas may be used individually to determine the presence and the concentrations of chemical components present in the air for those that are skilled in reading the color change reaction of the coated paper.
It has been found, however, that these individual chemically reactive papers have a short shelf life or may become fouled or unstable from contaminants such as dust or other materials. Such contamination can make the prior art color reactive papers un-useable for their stated purpose and non-reactive or at least less reactive to their target compound.
Further, chemical and other filtration systems can consist of sorbents such as activated carbon, impregnated activated carbons, zeolites, permanganate impregnated alumina and similar substrates collectively referred to as chemical media. During use, appropriate selected chemical media may remove malodorous, toxic and/or corrosive gases from the environment up to a certain finite life. For determining media change-out schedules, it is typical to estimate what portion of the media has been utilized and by extension when a necessary change-out date is determined. Previously, determination of media exhaustion has been done by coupon analysis (ISA methodology), gas challenge testing (ASTM 6646 or ASHRAE 145.1) and air quality analysis using instrumentation such as gas chromotography/mass spectrometry or gas chromatograph-flame ionization detectors, as well as portable electronic gas sniffers and detectors. A standard for testing remaining usable media capacity may utilize either the ASTM or ASHRAE methods which challenge a small portion of the chemical media with large concentrations of simulated gases in order to predict remaining life. The drawback to such accelerated testing is that it is not representative of contaminant concentrations which may be orders of magnitudes lower in real-life conditions. Lab testing further may not accurately simulate the variety of contaminants in the air in normal field conditions and are known to cross-interact and competitively reside on chemical media. Sophisticated portable electronic instrumentation may not aide in determination of media life due to the cost and time involved in analysis.